1. Field of the Invention
This invention relates to a radiation image read-out apparatus. This invention particularly relates to a radiation image read-out apparatus, wherein a radiation image is read out from a stimulable phosphor sheet, on which the radiation image has been stored and which has been taken out of a cassette, the stimulable phosphor sheet is then erased, and the erased stimulable phosphor sheet, which is now reusable for the recording of a radiation image, is returned into the original cassette.
2. Description of the Prior Art
It has been proposed to use stimulable phosphors in radiation image recording and read-out apparatuses. Specifically, a radiation image of an object, such as a human body, is recorded on a sheet, which comprises a substrate and a layer of the stimulable phosphor overlaid on the substrate (hereinafter referred to as a stimulable phosphor sheet). In a radiation image read-out apparatus, the stimulable phosphor sheet, on which the radiation image has been stored, is exposed to stimulating rays, such as a laser beam, which cause the stimulable phosphor sheet to emit light in proportion to the amount of energy stored thereon during its exposure to the radiation. The light emitted by the stimulable phosphor sheet, upon stimulation thereof, is photoelectrically detected and converted into an electric image signal. The stimulable phosphor sheet, from which the image signal has been detected, is exposed to erasing light or heat, and energy remaining on the stimulable phosphor sheet is thereby released.
The image signal, which has been obtained with the radiation image read-out apparatus, is subjected to image processing, such as gradation processing or frequency processing, such that a visible radiation image having good image quality can be reproduced from the processed image signal and used as an effective tool in, particularly, the accurate and efficient diagnosis of an illness. The processed image signal is then used for the reproduction of a visible image on a recording material. The stimulable phosphor sheet, from which the image signal has been detected, is erased and reused for the recording of a radiation image.
Ordinarily, the stimulable phosphor sheet described above is housed in a light-tight cassette. Each cassette serves to house a single stimulable phosphor sheet therein. At least part of the cassette can be opened in order for a stimulable phosphor sheet to be fed into and out of the cassette. The openable part of the cassette is releasably supported by a cassette support means of a radiation image read-out apparatus. In the radiation image read-out apparatus, the stimulable phosphor sheet, which is housed in the cassette supported by the cassette support means and on which a radiation image has been stored, is taken out of the cassette by a sheet conveyance means and conveyed into an image read-out means. The radiation image is then read out of the stimulable phosphor sheet. Thereafter, energy remaining on the stimulable phosphor sheet is erased by an erasing means, and the erased stimulable phosphor sheet is returned to the original cassette. Such radiation image read-out apparatuses are described in, for example, Japanese Unexamined Patent Publication Nos. 62(1987)-124549 and 63(1988)-298333.
However, with the radiation image read-out apparatus described above, a predetermined time is required for each of the operation for reading out a radiation image and the erasing operation. For example, when the stimulable phosphor sheet, from which an image signal has been detected, is being erased, the image read-out operation is ceased in the image read-out means. Therefore, in cases where images are read out and erased from a large number of stimulable phosphor sheets, a long waiting period occurs.